This application is related to application SC11501TP, entitled xe2x80x9cOptical Device and Method Therefor,xe2x80x9d and assigned to the assignee hereof.
This invention relates to opto-coupling and, more particularly, to integrated circuit device structures useful in opto-coupling.
One of the techniques used in opto-coupling is known as diffraction grating. This type of technique utilizes spaced grating features that provide a bend in the light so that the light is directed along a waveguide to an objective or from a source outside the waveguide. This is very desirable anytime there is a need to interface light between two points so that if light is being transmitted along a waveguide and is desirably sent outside of the waveguide or light is originating outside the waveguide and is desirably to be in the waveguide, a grating can be utilized to achieve this. One of the difficulties is that the grating is made up desirably of a number of grating features. The features must be spaced apart in a relationship that provides for the desirable bending to occur. This bending is dependent in a large measure on the frequency of the light. For the light to be effectively bent, the features have a certain spatial periodicity as well as the features themselves having certain desirable characteristics. In particular, higher frequencies require features that have a smaller period which effectively means they have to be closer together. This has been difficult to achieve in a manufacturable manner for the high frequencies that are being found to potentially useful in significantly improving the speed of integrated circuits.
Typically integrated circuit diffraction grating has been achieved by e-beam techniques. This is undesirable, although somewhat effective, because of the time required to achieve the patterning by e-beam. Also, the shape of the grating features is important. With the e-beam techniques the shape has been substantially limited to square and parallelogram type features. With respect to these individual grating features, it is important that the shape be predictable and that it have a shape which provides good coupling and transmission of the light between the waveguide and the grating. The feature must be smooth and consistent from one integrated circuit to the next. The spacing of the grating features is also coordinated with the shape. Typically these are used with polarized light because that is more efficient in the typical grating that has been provided in the prior art. Also smoothness has been difficult to achieve. So, there are situations where it may be desirable to not have to have polarized lights in which case the coupling would be very inefficient.
Thus, there is a need for a manufacturable technique for making a diffraction grating and a need for diffraction gratings of high quality.